The SIV won't come out next month, I can assure you that. First and foremost, because everything is a rumor at this point and over the last three years, Samsung releases their Galaxy S-series handsets in May or June, plus the fact that US carriers get these models typically at least two months later than the rest of the world, The earliest a US carrier will see the SIV is probably August.
The only thing you have to decide between the SIII and the Note is if you want the bigger screen size or not. The SIII's latest update gives it all the Note II features including multi-window. The only thing missing is the S-Pen (but than needs hardware support).